1. Field of the Invention
The present invention relates to a pressure switch comprising a diaphragm displaceable under pressure and a switch element responsive to the displacement of the diaphragm.
2. Description of Prior Art
There are known various pressure switch systems for vehicles. Japanese Laid-open Patent Application No. 56-54725 discloses one of these pressure switch systems which comprises a diaphragm displaceable under pressure, a movable contact responsive to the displacement of the diaphragm and a stationary contact co-operating with the movable contact to generate an electrical signal. Such a pressure switch system can relatively simply sense the variations in pressure and is particularly suitable for use in the vehicle engine as a negative pressure detection switch or the like. However, the use of a diaphragm requires a communicating opening formed in the switch body and which raises such a problem that moisture or external matters may enter the interior of the switch through the above communicating opening.
In the prior art switch system, moisture is prevented from entering the pressure chamber of the switch adjacent a pressure line by the use of a waterproof cap mounted thereon. However, the switch chamber of the system in the side opposite to the pressure chamber includes no waterproof means. Thus, the prior art switch system is disadvantageous in that the penetration of waterdrops causes the contacts to degrade in electrical conductivity, and so forth.